1. Field of the Invention
This invention relates to reflector antennas. More particularly, the invention relates to a polarization adjustment assembly for a reflector antenna that enables fine polarization adjustment.
2. Description of Related Art
Reflector antennas are highly directional. In addition to being closely boresight aligned with one another, reflector antennas and feed components contained therein forming an RF communications link are rotationally aligned with respect to signal polarity.
Rotational alignment improves polarization isolation, a signal quality factor that becomes significant, for example, where multiple signals are being transmitted/received each on a separate polarity. Reflector antenna mounting upon non-vertical mounting points, such as angled tower struts, is often required, introducing a rotational mis-alignment generally corresponding to the angle of the mounting point away from vertical. Prior reflector antennas, for example as disclosed in WO96/39726 “System for fine antenna-aiming adjustment on three orthogonal axes”, typically include fine adjustment capabilities incorporated into the mounting bracket. For polarization alignment, the system of WO96/39726 rotates the entire reflector antenna, including the reflector. Similarly, the system described in U.S. Pat. No. 6,433,757 “Antenna Polarization Adjustment Tool” provides a separate tool attachable to the antenna hub for general polarity alignment via rotation of the entire feed assembly.
Reflector antennas are typically installed at exposed locations high atop towers. Improved installation and/or maintenance personnel safety is a constant concern of the radio tower industry. Therefore, installation and/or adjustment procedures with a reduced number of steps and low installer force requirements are desired. Further, antenna specific tools are not desired as each additional tool presents an additional cost, separate drop hazard and ongoing inventory requirement.
Competition in the reflector antenna market has focused attention on improving electrical performance and minimizing overall manufacturing, inventory, distribution, installation and maintenance costs. Therefore, it is an object of the invention to provide a reflector antenna with a fine polarity adjustment capability that overcomes deficiencies in the prior art.